In the past, particulate matter has been loaded into vessels or dispensed by what is commonly referred to as the "sock" method wherein a hopper having an attached hose extends to the bottom of the vessel or to the surface of the previously dispensed particulate matter. The hopper and hose are filled with particulate matter and the particulates are released at the bottom the hose by slowly raising the hose to thereby permit the particulate matter to flow through the hose. The resulting dispensed particulates are in the shape of a cone which, during the dispensing of particulates, can be distributed over the entire given area by raking.
Commercial catalytic reaction zone vessels or reactors varying in width or diameter from about 1 foot to about 15 feet or more, having a length from about 5 feet to about 70 feet or more are loaded by the hereinabove described "sock" technique. One of the problems that is associated with loading reactors by this method is that the catalyst bed can contain excessive voids which can, during the use of the catalyst, bring about catalyst settling problems or "slumping", localized hot spots during the exothermic reactions of reactants and the necessity to utilize increased reactor volume. In addition, the sock technique requires increased times for loading a reactor since the hose through which the catalyst enters the reactor has to be continually adjusted upwardly in order to allow catalyst to flow. In addition to the above method, catalyst can be continually added through a hopper suspended above the catalyst surface which also results in the formation of a cone-shaped pile of catalyst upon the catalyst bed. As in the above method, the catalyst cone can be distributed over the catalyst bed by raking.
The resulting settling of the catalyst can change the overall volume of the catalyst bed thereby producing damage to equipment such as thermowells which have been inserted into the reactor for temperature measurements. In addition, the settling of catalyst can reduce the surface of the catalyst bed to a level whereby the thermowell is not in contact with the catalyst, thereby not allowing the reaction temperature to be monitored during the course of a reaction. Excessive voids in a sock-loaded, or otherwise inefficiently loaded, catalyst bed cause poor gas, liquid or gas-liquid distribution through the bed. The maldistribution often requires decreased throughput or increased temperatures, since the resulting catalyst utilization is low and product specifications may not be met. Settling problems associated with sock-loaded beds may result in damage to other reactor internals, such as baskets, redistribution trays, catalyst supports and quench spargers.
An additional problem associated with the previous loading techniques is that for a given reactor volume the amount of catalyst which can be charged is determined by the final catalyst density. Thus, a means for increasing the bulk density of catalyst present in a reaction zone would allow for increased throughput of reactants at the same severity or the same throughput at lower severity. Thus, more severe reaction conditions and/or increased throughput can be obtained for a given reaction zone volume if an increase in bulk density of the catalyst can be achieved.
Subsequently, those skilled in the art have used various dispensing apparatus which have demonstrated improved loading of particulates into reactor vessels. These prior art loading devices performed reasonably well for vessels having open spaces without obstructions which would interfere with the positioning of the loading device in or above the vessel, or would prevent the uniform free-fall of the distributed particulate matter.
Therefore, the known dispensing apparatus are not suitable for loading particulate matter into vessels which have a center-pipe located generally along the center line of the vessel. Those skilled in the art have sought to find a loading apparatus which produces a densely and evenly loaded bed of particulate matter in a rapid and facile manner.